Using complementary approaches of micronutrient deficiencies and mice for which responses to defined micronutrients was abrogated in T cells or antigen presenting cells, we identified a previously unrecognized role for retinoic acid and its receptor, retinoic acid receptor alpha in the control of T cell and dendritic cells function and development. Notably, we found that RA regulates pre-cDC differentiation and that vitamin A deficiency has major consequences on the development of mucosal dendritic cells. During this fiscal year our work further explored how the immune system adapts to various states of malnutrition and demonstrated that defined aspect of innate immunity could be boosted to compensate for defective adaptive immunity under these settings. We also developed novel models of nutrient deficiency and integrated the exploration of the microbiota to these questions.